A multicast broadcast service is a point-to-multipoint communications method whereby identical data packets are transmitted simultaneously to multiple receiver nodes. As may be appreciated, receiver nodes may encounter packet losses—for example—due to channel impairments. As a result, retransmission of affected packets is oftentimes required.
A characteristic of such a retransmission scheme when used with a multicast service is that since each receiver generally experiences a different quantity of packet loss(es), a large number of retransmissions are required for each and every receiver to recover all lost packets. As is known in the art, the number of retransmissions can be reduced significantly if a coding scheme is employed which generates the retransmitted packets by an encoding across information packets. Advantageously such schemes enable each receiver to recover packets destined for that receiver based upon the received packets.
For example, in a paper entitled “ON THE MINIMUM NUMBER OF TRANSMISSIONS IN SINGLE-HOP WIRELESS CODING NETWORKS”, which appeared in PROC. IEEE INFORM. THEORY WORKSHOP, at Lake Tahoe, Calif. on September 2007, pp. 120-125, S.Y EL REOUAYHEB, M. A. R. CHAUDHRY, and A. SPRINTSON described a fundamental problem associated with finding an optimal encoding of broadcasted packets to minimize the overall number of retransmissions. Notably, the authors assumed in that a transmitter knows the indices of lost packets for every receiver, which unfortunately requires a large overhead on the uplink feedback channel. In “NETWORK CODING-BASED RETRANSMISSION SCHEMES FOR E-MBS WITH AND WITHOUT MS FEEDBACK”, which appeared in IEEE C802.16.m-090072r1, made available at URL http://wirelessman.org/tgmcontrib/C80216m-09.0072r1.ppt, H. XU, S. XU, N. ARULSELVAN, and S. KALYANASUNDARAM describe several network coding-based retransmission schemes for a broadcast service without requiring feedback from receive nodes.
Notwithstanding these developments, an improved retransmission and coding scheme for multicast broadcast services would represent a significant advance in the art.